This invention relates to a method of making and using packaging material for perishables, such as fresh meats, processed meats, fish, cheese and the like. More particularly, this invention relates to a film material and a method for packaging with such film material to extend the storage time and prevent spoilage of fresh bulk cuts of meats (which are referred to as primal and sub-primal cuts) which are vacuum packaged by providing a visual inspection system whereby improperly sealed packages are immediately recognizable.
In the past, many producers of films have used various types of film composites, such as a composite of Ethylene Vinyl Acetate (EVA)/Polyvinylidene Chloride (PVDC)/Ethyl Vinyl Acetate (EVA), Polyvinylidene Chloride (PVDC)/Polyvinylchloride (PVC) co-polymer, or nylon/Surlyn (DuPont ionomer), to manufacture bags for preserving bulk cuts of meats and other perishables. Most of the bags are formed from composite films made from two sheets of the composite film or formed into tubes.
It has been found that bags manufactured from the nylon/Surlyn composite film provide all the desirable characteristics for preservation and storage of meats and other perishables. However, the presently used nylon/Surlyn film is produced by co-extrusion. Again, it has been found that the bond between the co-extruded nylon/Surlyn is of low quality and inconsistent. For example, the bond strength of a presently known co-extruded nylon/Surlyn varies from 30 to 80 grams per inch of width. Nevertheless, one of the advantages of co-extruding the nylon/Surlyn film is the avoidance of the so-called "flash wrinkles" which create random lines of weakness in the nylon film, which occur when extrusion coating nylon film with a sufficient quantity of heat sealable plastic. The cause of the flash wrinkles is believed to be the rapid absorption of heat from the mass of molten heat sealable plastic.
When using bag film web material, the webs are cut into proper size sheets and are sealed together on three sides to form a bag while the tube type structures are sealed and cut into bags into which the meat cut is placed. Generally, the producers strive for a totally transparent or clear bag material so that, when used to package meat, the fresh meat color can be seen through the bag. When using this type of bag material, normally a dusting process is used to introduce a non-sticking substance, such as some form of starch dust (corn starch) onto the contacting inside surfaces of the bag to prevent the inside surfaces of the bag from sticking together due to static electricity or cohesion and blocking, thus, permitting the bags to be opened more easily to introduce the meat cuts.
After the meat cut is placed into these presently known bags, the bags are placed in a standard vacuum sealing chamber where a vacuum is drawn on the bag. The open end of the bag is sealed to completely seal the bag while in the vacuum chamber. Although this method of packaging has been widely used, there are some disadvantages which the present invention will eliminate. The present invention also avoids the flash wrinkle problem which usually occurs when extrusion coating nylon film with a sufficient quantity of molten thermoplastic material makes storage bag structures.